A carbon nanotube (CNT) has a tube structure in which carbon atoms are combined with others in a form of a hexagonal lattice. The carbon nanotube may have a diameter of several nanometers. The carbon nanotube may be known as a defect-free material having superior mechanical strength, high electrical selectivity, excellent field-emission performance, and efficient hydrogen storage capability. The carbon nanotube is usually manufactured by high synthesis technologies such as arc discharge, pyrolysis, laser deposition, plasma enhanced chemical vapor deposition, thermal chemical vapor deposition, electrolysis, and flame synthesis.
Efforts to use the aforementioned properties of the carbon nanotube have been made in a variety of fields. For example, U.S. patent Publication No. 2003/0100189 A1 discloses a method of forming a catalyst metal on a substrate and growing a carbon nanotube thereon. At least one problem with the method disclosed in this document is that it is difficult to obtain a carbon nanotube vertically oriented against the substrate.